1. Field of the Invention
The present invention concerns a system and device for rendering a sailboat comfortable and safe from danger of capsizing, and more specifically relates to a sailboat with a mast which can be either automatically or manually pivoted to port or starboard.
2. Description of the Related Art
A sailboat is basically comprised of a hull having bottom, bow and stern portions, a deck, and at least one mast for supporting a sail extending above the deck. The mast is traditionally rigidly set so as to remain in the same relative position with respect to the hull. A fixed keel extends from the bottom, and a ballast is rigidly formed to the keel to aid in stabilizing the hull. The keel is heavily weighted to provide a substantial amount of ballast to add stability to the sailboat when under way. Wind acts upon the sail and the sail bears upon the mast, occasioning the forward travel of the sailboat, and also incidentally deflecting the mast to the leeward side so that the leeward edge of the sailboat is depressed towards the water level. As the sailboat heels further, asymmetrical underwater hull shape tends to cause veering of the craft off-course while increasing the bow wake and resistance to forward movement.
The traditional fixed mast arrangement is generally regarded as providing a measure of safety and security. That is, it is perceived that as the sailboat keels over, fixed ballast down low will reliably lever the boat back towards vertical. However, if the force of the wind acting upon the sail is too strong, even a heavy ballast will not prevent the sailboat capsizing.
The three primary factors effecting a sailboat are buoyancy, gravity, and wind. Buoyancy can be modified to improve stability by modifying the shape of the hull, i.e., by increasing displacement to port and starboard as in the case of a catamaran. However, such an approach reduces the habitable space of the sailboat, thus is not a practical approach.
Attempts have also been made to improve sailboat stability and safety by addressing ballast. Sailboat crews have long been employed as movable ballast, moving to windward as the sailboat heels thereby to prevent the hull from capsizing and to maintain the stability of the hull. However, as the hull heels further and further over, the crew weight is moved closer to being over the center of buoyancy of the sailboat, the effect of the righting arm decreases, their effectiveness as ballast is lowered, and the further the boat heels, the less stable the boat becomes, until it ultimately capsizes.
Proposals have been made to use an articulating keel with ballast mounted at the bottom of the keel. In theory, ballast provided at the bottom of an articulating keel can be moved as needed to port or starboard so that the center of gravity of the sailboat is moved further windward of the center of buoyancy, increasing the righting arm. For purposes of speed, it makes sense to move the keel weight sideways, saving weight while keeping hull, rig and underwater foils in their most effective vertical mode. However, such a system adds significantly to the cost of a sailboat and to the complexity of sailing. Tilting the keel centerboard off-vertical decreases the plane of the centerboard against the water, increasing the sideways-to-forward movement ratio of the sailboat. Further, as the sailboat heels over to near the point of capsize, the movable keel can do nothing to help right the sailboat, since in that orientation of the hull the movable keel substantially corresponds to the position of a fixed keel/fixed ballast sailboat. That is, with a traditional sailboat, the greater the heel, the greater the effect of the ballast. Further yet, a movable keel is not visible, and a keel tilted in the wrong direction, particularly in a situation such as an emergency change of tack, will readily result in capsizing.
U.S. Pat. No. 3,972,300, shows a sailing craft having a one-piece hull design with a unitary mast, keel, and ballast assembly mounted on the hull of the craft so that the mast, keel, and ballast assembly can rotate independently on the hull to permit the hull of the craft to float free of the wind heeling forces. In U.S. Pat. No. 3,885,512, a catamaran structure is shown in which the mast and sail are also formed as a unitary structure to tilt laterally to port or starboard when the catamaran is underway. The unitary structure of the mast and the keel are rotatably mounted to the platform above the water level in the catamaran.
U.S. Pat. No. 5,280,760 teaches a sailing craft in which a mast is rigidly connected to a keel via a transfer shaft having a pivot axis along the bottom of the hull of the sailboat, and in which the rigid mast and keel assembly is mounted for side-to-side movement relative to the hull. Ballast is provided at the bottom of the keel. Movement of the mast from side-to-side rotates the keel in the opposite direction from the mast to stabilize the sailboat. There is an increase in safety, since any increase in wind on the sail causes the sail to tilt without heeling the sailboat hull. However, on closer analysis, it can be seen that the gain in stability from pivoting the keel and mast is at great cost. First, the righting moment due to the change in center of buoyancy which occurs with heeling of a conventional fixed-mast sailboat is lost, since the hull effect is not transmitted to the mast. Second, since the effect of wind on the sail must be counteracted by an opposite action of the ballast of the keel, and since the vertical keel is at equilibrium and imparts no righting moment, this sailboat can not be sailed with the mast vertical. Rather, the mast will always tilt until equilibrium is reached between, on the one hand, the force of wind urging the sail to leeward, and on the other hand, the force of gravity tending to cause the offset ballast of the keel to return to vertical. Thus, this system is far from optimal.
U.S. Pat. No. 3,885,512 is similar in principle to U.S. Pat. No. 5,280,760, except that the principle is applied to a catamaran structure.
The third approach, after buoyancy and ballast, has been with respect to movement of the sails. U.S. Pat. No. 241,037 teaches a sailboat rendered more capsize proof by providing a pivotably mounted mast kept perpendicular to the hull by means of springs. The force of wind acting upon the sails causes the springs to give and the mast to be tipped transversely to port or starboard. While this may appear to improve safety in the case of a sudden gust of wind, on closer examination it can be seen that this system has a number of disadvantages, including the fact that the mast is most caused to pivot when least needed, i.e., when the sailboat is vertical and the force of wind on the sail is strong. The mast is least likely to give and pivot when most needed, i.e., in the final arc of heel in which the sailboat is nearest capsizing. In fact, the system is actually dangerous, in that as the sailboat heels over, the force of the wind on the sail is reduced, and as the sailboat comes close to capsizing, the springs urge the mast to a more upright position to catch more wind, thus increasing the tendency to capsize at precisely the time when what is needed is a lessening of wind force on the sails.
U.S. Pat. No. 273,529 teaches a mast and spar arrangement wherein the sail is permitted to set off from the mast to leeward, better enabling the boat to tip up to the wind. As the boat keels to leeward, the offset sail is more upright than the mast, and gets more benefit from the wind. However, while increasing the speed and ability to capture wind, the arrangement does not improve safety. In fact, the arrangement causes the sail to receive more wind as the sailboat careens or heels, increasing the likelihood of capsizing.
U.S. Pat. No. 641,321 teaches a sailboat in which a mast is mounted so as to remain perpendicular to the hull, yet so mounted so as to be capable of being relocated either port or starboard of the centerline of the sailboat. This has a beneficial effect with regard to the relationship of the wind force vector and the weight of the mast and sails to the center Of gravity of the sailboat and the center of buoyancy of the sailboat. However, there is no improvement with respect to safety, as this sailboat, once heeled, is as likely to capsize as a conventional sailboat.
U.S. Pat. No. 4,005,669 teaches a mast displacement mechanism comprising a cradle supported by the hull and defining a track structure. The upper end of the mast is connected via cables to port and starboard points on the deck, such that the mast can pivot about a pivot axis defined by the attachment points of the cables to the mast. The cradle is of radius and curvature that the lower end of the mast rests in and is free to move to port and to starboard on the track of the cradle. The pivot for the tilt of the mast is located at the upper zone of the mast, as a pendulum, and the lower deck end of the mast is capable of moving through and arc, guided by the track means along a radius of curvature between the pivot and track means. This mast displacement mechanism permits the sailboat to point closer to the wind, to better utilize hull forms, and to minimize list under varying wind conditions. However, the range of adjustment of the sail is necessarily constrained by the length of track confined by the hull.
While the above mentioned patents are representative of the designs which have been developed to provide sailboats of improved stability and safety, each of the known approaches has significant disadvantages which offset the purported advantages. Further, the above described systems and devices are generally too mechanically complex for retrofitting of existing sailboats.
There remains a need for a sailboat mast adjustment system and means which is easy to understand and use, inexpensive, and capable of being retrofitted on existing sailboats.